18.
Place parentheses in the following equation to
make it true.
4 + 53-8 = 19

(4+5)3-8 = 19

Step-by-step explanation:

1) You know that the parenthesis are going to go around 3-8 or 4+5 because that is the only way multiplication is involved. If you put them anywhere else it doesn't change the answer.

2) Try solving the problems (use PEMDAS)

(4+5)3-8 = 9*3-8 = 27-8 = 19

4+5(3-8) = 4+5(-5) = 4-25 = -21